Relaxation dynamics of bola-shaped smectic island in a thin, spherical bubble of smectic C liquid crystal in microgravity

We describe the relaxation dynamics of an elongated SmC* island embedded in a dense, two-dimensional emulsion of circular islands on a spherical liquid crystal bubble. Four-lobe extensional shear flow driven by air jets creates a bola-shaped inclusion comprising two roughly circular reservoirs connected by a long, extremely thin strip in the background island emulsion. After shear flow ceases, the bola relaxes slowly to become a single, circular domain. The connecting strip between the two islands gradually becomes shorter, eventually forming a broad bridge connecting the islands, which then proceed to merge, first transforming into an elliptical inclusion and then a single circular island. The dependence of the thin stripe length on time allows us to estimate the island mobility μ assuming the force acting on the islands are due to the line tension of the strip. The measured viscosity, particularly during the coalescence phase, is larger than expected from simple estimates of the dynamics on a uniform background film, an effect we suggest is probably related to additional drag from the background island emulsion.